1. Field of the Invention
This invention relates to a method and apparatus for distinguishing aperiodic noise input signals from periodic input signals during measurement, and is of particular utility for analysis of the operation of a timepiece.
2. Description of the Prior Art
In certain prior systems for measuring the accuracy of a running timepiece, the oscillating cycle of a time-keeping resonator, for instance of a balance wheel, tuning fork or the like is compared with the cycle of a reference oscillation. It is thus possible to determine whether the oscillating cycle of the time-keeping resonator is correct or not.
In another prior measuring system, the number of cycles of a high frequency reference oscillator is counted during one cycle or a small number of cycles of the oscillation of a balance wheel of a watch to be tested. In this system the counting time is determined by means of a microphone which detects the noise of the escapement driving the balance wheel, the amplified pulses from the microphone being used for starting and stopping counting of the reference frequency. However, in such a system, not only the desired periodic pulses produced by the escapement but also background noises may be detected by the microphone, it being difficult to eliminate such parasitic noises which are often sensed by the system as the beginning or end of the counting interval thereby falsifying the measuring result.